Temperatures well below freezing can strip a battery of half its power. An automotive parts specialist explains the five main culprits and how drivers can protect themselves.
Few experiences are more frustrating than turning the key on a cold morning and hearing nothing. Yet for many drivers, a flat battery in winter comes as a genuine surprise – despite the fact that low temperatures are among the most well-documented causes of battery failure.
Kazimieras Urbonas, Supplier Excellence Manager at Ovoko, a major European marketplace for used car parts, says demand for replacement batteries rises noticeably each time temperatures drop. “Drivers often don’t realise how much cold weather affects their car’s power system until they’re stuck with a dead battery,” he said.
Below, Urbonas identifies the five main reasons batteries fail in cold conditions – and what drivers can do to reduce the risk.
1. Cold Slows the Battery’s Chemistry
The most fundamental problem is physical. A car battery generates electricity through chemical reactions, and those reactions slow down as temperatures fall. At 0°C, a battery’s output can drop by around 20 percent. At -17°C, it can lose between 40 and 50 percent of its effective strength.
“The chemical reactions that create electricity literally slow down when it’s cold,” Urbonas said. “Your battery is working twice as hard to deliver the same amount of power.” At the same time, a cold engine requires more effort to turn over – meaning greater demand meets reduced supply.
2. Heating Systems Place Heavy Electrical Demands on the Battery
Heated seats, the blower fan, the front demister, and the rear window heater are all standard responses to a cold morning – and all draw significantly from the battery, particularly on short trips where the alternator has little time to compensate.
Urbonas puts the numbers in context: heated seats can draw three to five amps each, while a heater blower running at full power uses a further ten to fifteen amps. “Add in your demister and rear window heater, and you’re looking at a serious drain on your battery’s reserves,” he said. The problem is compounded by the fact that drivers are most likely to use all these systems simultaneously in precisely the conditions that already stress the battery most.
3. Short Journeys Prevent the Battery from Recovering
Starting a car engine draws a significant burst of current – typically between 100 and 200 amps over a matter of seconds. Replenishing that charge is the alternator’s job, but it needs time. Urbonas says a minimum of 20 to 30 minutes of driving is required to fully recover the energy used during a cold start.
For drivers whose typical journeys run to ten minutes or less, the arithmetic is unfavourable. “Each short journey leaves your battery a little weaker than before,” he said. “It creates a downward spiral that can take weeks to become apparent.”
4. Plugged-In Electronics Create a Continuous Drain
Dashcams, phone chargers, and portable sat navs all draw power even when the engine is off – a phenomenon known as parasitic drain. Individually, the current involved is small. A dashcam might draw as little as 0.1 amps. But over several days of a car sitting unused in cold weather, those small draws accumulate.
“In cold weather, when your battery is already struggling, even small drains can push it over the edge,” Urbonas said. Unplugging accessories when parking is a simple precaution that many drivers overlook.
5. Older Batteries Have Less Margin for Error
Most car batteries have a serviceable life of three to five years. As they age, their capacity diminishes and their internal resistance increases – both of which become more pronounced in cold conditions. A battery that performs adequately in mild weather may fail entirely when temperatures fall.
“If your battery has already lost some of its capacity, cold weather will make that loss far more noticeable,” Urbonas said. Symptoms to watch for include slower engine cranking and dimmer headlights – signs that a battery is struggling before it fails completely.
Practical Steps to Reduce the Risk
Urbonas offers several measures drivers can take before cold weather becomes a problem.
Where possible, parking in a garage – or using an insulating battery blanket in extreme conditions – keeps the battery warmer and preserves its output. On short trips, limiting the simultaneous use of high-draw systems such as heated seats and the blower fan reduces the load on an already taxed battery. Unplugging accessories when the car is parked removes a source of ongoing drain.
Taking the car on a run of at least 30 minutes at regular gives the alternator time to properly recharge the battery, and is particularly important for drivers whose day-to-day journeys are short. For vehicles that sit unused for extended periods, a trickle charger can maintain the battery’s charge without the risk of overcharging.
Urbonas also recommends having the battery tested before the coldest months arrive. “Most auto parts stores will test it for free,” he said. “It’s much cheaper than a roadside rescue.”
The broader point, he suggests, is that most cold-weather battery failures are foreseeable. “By the time your car won’t start, the problem has usually been building for a while. With proper care, most batteries can handle cold weather just fine.”
